Air sleeves have a rubber innerliner, two plies of cord fabric, and a rubber cover. These sleeves see their greatest commercial usage in the automotive helper spring market by being mounted as air springs on shock absorbers and struts. Other uses include truck cab suspension springs, truck driver seat springs, automobile air springs, and a variety of industrial air springs.
The air sleeves are manufactured with a variety of ends, but these ends fall into two basic constructions: those with the ending of the cord plies exposed to the air (usually a cut end), and those where the endings of the cord plies must be completely encased in rubber, called a `sealed end`. For sealed end sleeves, enclosing the cord endings in rubber is very important if the end of the sleeve is exposed to the high pressure air chamber of the air spring, where exposed cord ply ends may lead to sleeve failure due to high pressure air entering the exposed cord endings and migrating into the body of the air sleeve.
Another common requirement for air sleeves is that the cord ply endings be within 0.20" or less (5.1 mm or less) of the sealed end of the part. This requirement relates to the air shock manufacturer's need to avoid excess material beyond the end of the crimp fastener, the need to crimp very near the end of the part, and the need to have a good crimp which requires the cord plies to end very near the end of the sleeve.
However, in manufacturing air sleeves with sealed ends, several issues may arise. First, some sealed end air sleeves require not only that the cord endings be placed within 0.20" or less (5.1 mm or less) of the end of the part, but also require a chamfered angle on the end of the part of typically 30.degree. to 60.degree., which reduces the thickness of the end of the part by up to 50%. The combined requirement for cords to be adjacent to the end and the chamfered shape can make it very difficult to reliably seal the cord endings during the molding process because of the loss of covering rubber due to the chamfer.
Secondly, if the molding process uses an inflatable bladder on one side of the part and a metal mold on the other side of the part, significant movement of the end areas of the air sleeve as the bladder inflates can occur. This can lead to the cord endings drifting toward one surface of the part, while the elastomer is soft and flowing. This may result in unreliable sealing of the cord endings.
Thirdly, some air sleeve must be provided with a firm or stiff end to the part. This goal may be difficult to achieve if a sealed end, or a sealed and chamfered end is also required. The lack of cords extending completely to the end of the part reduces the stiffness, and chamfering significantly reduces stiffness.